Method to monitor additive manufacturing process for detection and in-situ correction of defects

ABSTRACT

The present invention provides a system and a method for real time monitoring and identifying defects occurring in a three dimensional object build via an additive manufacturing process. Further, the present invention provides in-situ correction of such defects by a plurality of functional tool heads possessing freedom of motion in arbitrary planes and approach, where the functional tool heads are automatically and independently controlled based on a feedback analysis from the printing process, implementing analyzing techniques. Furthermore, the present invention provides a mechanism for analyzing defected data collected from detection devices and correcting tool path instructions and object model in-situ during construction of a 3D object. A build report is also generated that displays, in 3D space, the structural geometry and inherent properties of a final build object along with the features of corrected and uncorrected defects. Advantageously, the build report helps in improving 3D printing process for subsequent objects.

FIELD OF THE INVENTION

The present invention generally relates to the field of additivemanufacturing process or 3D printing of objects, and more particularlyto a method for real time monitoring, detecting and correcting defectsduring the additive manufacturing process.

BACKGROUND

The additive manufacturing process is widely known as the threedimensional printing of 3D objects. Numerous methodologies have beendescribed in prior art, the most common including solid-laser-sintering(“SLS”), stereolithography (“SLA”), and extrusion based 3D printing orFFF (fused filament fabrication). Extrusion-based 3D printing involvesthe deposition of thermoplastic materials. Prototyping is the mostcommon application of extrusion-based printing today, using materialssuch as ABS (acrylonitrile butadiene styrene) and PLA (polylactic acid).Further, the technologies have progressed to where the 3D printing alsoutilizes higher-end engineering semi-crystalline and amorphous polymersas well as metals and ceramics with greater mechanical, chemical,thermal and electrical properties. Examples of semi-crystalline polymersinclude polyetheretherketone (PEEK), polyetherketoneketone (PEKK), etc.Examples of amorphous engineering polymers include polyphenylsulphone(PPSU), polyetherimide (PEI), etc.

Prior art for extrusion based 3D printing teaches extruding the filamentthrough an extruder and depositing the extrudate on a build platform, alayer at a time to form a 3D object in open loop with no feedbackconcerning the build process or quality of deposition. As a result,defects in the 3D object printing lead to one or more errors in itsgeometry (i.e. dimensions or contours) or deficiencies in desiredproperties (e.g. mechanical, chemical, thermal, or electricalproperties).

These defects, errors, or characteristics that depart from the intendeddesign, due to deviation in filament diameter, filament feed rate,nozzle orifice, result in inaccurate volume of extrudate deposition;inaccuracy in the print head to follow the desired tool path causing outof tolerance features; deviation in heating or cooling temperature ofthe deposited material resulting in defects such as drooping/sagging,reduced crystallinity, slow solidification, air bubbles, delamination,overhangs, warping, or poor adhesion between printed layers of theobject or the build plate. Hence, these defects if not corrected, leadto flaws, such as insufficient mechanical, chemical, thermal, orelectrical properties, in the printed object.

One of the 3D printing methods used is illustrated in FIG. 1. A slicingsoftware slices a 3D object file (100) into a number of layers (102)using slicing parameters such as filament diameter, nozzle orifice,layer thickness, fill ratio, print head speed etc. Tool pathinstructions (104) are generated for each layer and are fed to a 3Dprinter where each layer is printed without any means to monitor, detector correct errors or modify slicing parameters based on analysis ofprinted layers. If the printing of the layers to build the object isfinished (106), the printing stops (108). Otherwise, the method loopsback to printing next layer by the extruder (104).

The prior art do not disclose providing a quantitative and qualitativereport that may inform a user of the 3D printing process about thestructure of the printed object along with the features of the defectsand further, guide the user to keep or scrap the object. Also, suchreports guiding in improving the printing of three dimensional objectsare lacking in the prior art.

Therefore, there exists a need in three dimensional printing methods formonitoring and identification of defects formed in a 3D object while itis being printed, and further, in-situ correction of the defects in theobject simultaneously as the object is being printed. There also existsa need for a closed-loop slicing engine that updates the slicingparameters and object model in-situ, based on the defect data and objectgeometry. Furthermore, there exists a need in three dimensional printingfor developing a report displaying geometry and the features ofcorrected and uncorrected defects in the 3D printing processes forimprovement in the printing.

SUMMARY OF THE INVENTION

The present invention provides an improved method of additivemanufacturing comprising monitoring and identification of defectsoccurring in a 3D object while it is being printed; in-situ correctionof defects in the object based on a quality control feedback whileprinting process; and updating slicing parameters and object model basedon the correction. A 3D object segment or layer is sliced based onslicing parameters and object property requirements. Tool pathinstructions for segment or layer are generated and fed to 3D printerfor printing. Quality of printed segment, layer, or build feature (i.e.through-hole, overhang, contoured section, etc.) is analyzed fordefects. If it is possible to correct the defects, tool path isgenerated for a particular tool, with a capability such as milling,drilling, heating, and extrusion etc., attached to a head capable offollowing multi-dimensional path.

Next, the object model and slicing parameters are updated based onanalysis of previously printed segment, layer, or build feature,including defects and corrected defects. A qualitative and quantitativereport for the segment, layer, or build feature is generated. Thisreport also logs monitored parameters such as temperature, speed, amountof material used, and any imaging data. Once the object is completelyprinted, a final report including property analysis is generated. Finalreport verifies whether or not the object meets intended properties andbased on the in-situ parameter adjustments during build, it recordsmodified tool path instructions for next build.

An objective of the present invention is to provide a system ofmonitoring, identifying and correcting defects, while also updating toolpath instructions and object model in-situ during the formation of 3Dobjects, effectively adding a closed loop feedback system for partquality.

An objective of the present invention is to provide a method ofmonitoring, identifying and correcting defects, and updating tool pathinstructions and object model in-situ during the formation of 3D objectsprinted, effectively adding a closed loop feedback system for partquality.

An objective of the present invention is to provide a plurality offunctional tool heads having multi-axes motion mechanism that areindependently and automatically controlled to perform one or morefunctions that are based on a feedback analysis for correcting thedefects.

Another objective of the present invention is to provide a means forlogging real time events such as identified defect information, criticalfeature measurements, dimensionality, contour of the printed 3D object,location of the defects and the correction mechanism taken.

Another objective of the present invention is to generate a build reportlisting the defects (both corrected and uncorrected) in the printed 3Dobject and using the build report for predicting properties of the finalbuild part, such as mechanical strength, electrical and/or thermalconductivity, chemical resistivity, EMI/ESD sensitivity, etc. The buildreport can also be used to optimize the build parameters and tool pathfor this build object to minimize the presence of defects in futureruns.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a flow diagram showing one of the conventional waysof performing additive manufacturing to build 3D objects.

FIG. 2 illustrates a system showing a logic flow of a closed feedbacksystem for printing 3D objects using additive manufacturing method, inaccordance with an embodiment of the invention.

FIG. 3 illustrates a flow diagram depicting a relation between a slicingengine and functional tools of a 3D printing machine, including anextruder, in accordance with an embodiment of the present invention.

FIG. 4 illustrates a part of the system 200 for analyzing 3D printedobjects, repairing defects generated during printing, and updating toolpath instructions and object model, in accordance with an embodiment ofthe present invention.

FIG. 5 illustrates a table showing the types of defects, the techniqueby which it is detected and suggested course of action for correctingthe defect, in accordance with an embodiment of the present invention.

FIG. 6 illustrates an exemplary illustration wherein functional toolheads are attached to a plurality of robotic manipulators used inadditive manufacturing method, in accordance with an embodiment of thepresent invention.

FIG. 7 illustrates a flowchart showing a method of additivemanufacturing to print a 3D object with monitoring, identifying andcorrecting defects in the printed 3D object, in accordance with anembodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In the following detailed description of embodiments of the invention,numerous specific details are set forth in order to provide a thoroughunderstanding of the embodiment of invention. However, it will beobvious to a person skilled in art that the embodiments of invention maybe practiced with or without these specific details. In other instanceswell known methods, procedures and components have not been described indetails so as not to unnecessarily obscure aspects of the embodiments ofthe invention.

Furthermore, it will be clear that the invention is not limited to theseembodiments only. Numerous modifications, changes, variations,substitutions and equivalents will be apparent to those skilled in theart, without parting from the spirit and scope of the invention.

The present invention provides a system and a method for additivemanufacturing process to build or print a 3D object/part that includeand is not limited to three dimensional printing methods, such asextrusion based, fused filament fabrication, droplet based, jettingmethods and the like. More particularly, the invention provides a systemand a method to monitor the printing process and identify, in real time,defects occurring in an object while it is being printed through theadditive manufacturing process and further, in-situ correcting thedefects, in real time, in order to produce a printed 3D object, whichmeets the intended specifications (e.g. geometrical, mechanical,chemical, or thermal, or electrical).

During additive manufacturing or three dimensional printing processes,incorrect or inaccurate building of the part can occur. This means, thatduring such printing processes, defects in the structural geometry ofthe part are incurred and may also diminish its inherent or intendedproperties. This may occur, for example, if the printing processes lackaccuracy in deposition of building material by a print head whileprinting the object, or lack insufficient feedback analysis that canidentify one or more defects occurring in the object while it is beingprinted. Hence, many objects/parts may get incorrectly built and thefinished part will not meet its intended specifications. Becauseextrusion-based systems are high dynamic not only at the system levelbut also at the fluidic level, certain instances of defects areinevitably unavoidable.

Therefore, the present invention provides a system and a method forefficiently monitoring the printing process and identifying the defectsin the object, in real time. Further, the invention provides a mechanismto correct the defects, in real time, simultaneously while the object isbeing printed. Furthermore, the invention provides a mechanism foranalyzing the data collected from the detection devices and updatingtool path instructions and object filament model in-situ during theconstruction of a 3D object.

FIG. 2 illustrates a system showing a logic flow of a closed feedbacksystem for printing 3D objects using additive manufacturing method, inaccordance with an embodiment of the invention. A user may input desiredcharacteristics of a 3D (three dimensional) object that needs to beprinted along with its inherent properties, through a user device. Thecharacteristics inputted by the user may be object properties that arerequired in a final object, including and not limited to physicalgeometry of the object, along with inherent properties like mechanical,electrical, chemical, and/or thermal properties and features that arerequired to build the object. The user device contains a 3D modelingprogram, which may be used with a 3D data file 202 that defines theproperty requirements 204 b of the printing object. In an embodiment,the user device may contain programs such as AutoCad, wherein the usermay prepare a CAD file defining the characteristics of the 3D object,including geometrical, mechanical, thermal, chemical, electrical andother property constraints of the object. In an embodiment, the 3D datafile 202 may be a CAD file, or an STL file or a COD file, and the like.The user device uses conventionally available techniques to create ablue print for printing the 3D object. Thereafter, the 3D data file 202is fed to a first engine, such as a slicing engine, of the system 200for discretizing the 3D data file 202 into a plurality of segments alongarbitrary planes. Additionally, the slicing engine is also capable ofdiscretizing the 3D data file 202 into a number of slices along twodimensional planes. A set of tool path instructions 206, therefore, arethen formulated using the slicing engine, by implementing propertyanalyzing techniques and involving a set of slicing and materialparameters 204 a and object property requirements 204 b. One embodimentof the present invention may employ finite element analysis as theproperty analysis method.

The determined tool path instructions 206 are further adopted by a toolof a printing or build apparatus to print the object. The tool pathinstructions 206 generated by the slicing engine are the set ofinstructions that are followed by a material extruding tool head forbuilding a 3D object. Therefore, the extruding tool head may deposit anumber of printable layers of building material (as shown by 208)following the tool path instructions 206 for printing 3D object. Also,the tool path instructions 206 may be modified in-situ during theconstruction of a 3D object, where the modification is based on afeedback analysis that is generated from a set of data collected by oneor more detection devices.

The system 200 further comprises a build apparatus that is used forprinting the 3D object. The build apparatus comprises a printingplatform where the three dimensional printing of the object is carriedout. The build apparatus may be in communication with the user device inorder to receive controlling signals or tool path instructions 206 fromthe user device. The build apparatus may further comprise a plurality offunctional tool heads with plurality of tool attachments that performdifferent functions associated with and required in the 3D printingprocess. The plurality of functional tool heads are attached tomulti-axis motion mechanism for providing movement of the tool heads inarbitrary manner, for example in x, y and z-axis. The tool attachmentsattached to the plurality of functional tool heads perform a variety offunctions that may include but are not limited to printing the object bydepositing the building material layer by layer while also providingsupport in printing the object, such as milling bit, deburring tool,cooling means, heating means, and the like.

Furthermore, the tool attachments also have the ability to orientthemselves with multiple degrees of freedom since they are attached tofunctional tool heads provided with multi-axis motion mechanism. For aperson skilled in the art, it may be obvious that multi-axis motionmechanism, such as robotic arms or manipulators, are present in the artto provide attachment for a number of tool attachments and allow them toperform various functions. In an embodiment, the functional tool headsalong with tool attachments may have more than one, such as 5 or 6,degrees of freedom of motion.

In a further embodiment of the present invention, one of the toolattachments may act as an extruder or print head or an extruding channelfor depositing material for the additive construction, while the othertool attachments may perform other ancillary functionalities such ascooling, heating, deburring, milling etc. The tool attachments of thebuild apparatus may function based on the tool path instructions 206,and are controlled by a controller. Further, each of the toolattachments may be independently controlled by the controller based onthe type of tool path instructions 206 accorded to each tool attachmentdepending on the type of function it performs.

In an embodiment of the present invention, the tool attachments performprinting and corrective functions, and may comprise a materialdeposition head, laser for heating, milling bit, deburring tool, coolingmeans, heating means and other tools with different functionalities usedin 3D printing process.

In an exemplary embodiment, only one of the tool attachments attached tothe functional tool heads may perform as print head that extrudesbuilding material to print the object; while the other tool attachmentsmay perform as correction devices. The functional tool head whose toolattachment is working as a print head for the printing apparatus may bereferred to as ‘first functional tool head’ or an ‘extruding head’,extruding printable layers of building material on the printing platformto print a 3D object. Hereinafter, the first functional tool head andextruding head may be used inter exchangeably. Further, the extrudinghead may be controlled by a controller to extrude material depending onthe tool path instructions 206 generated by the slicing engine.Therefore, to accomplish this, the user device sends the evaluated toolpath instructions 206 to the controller that further controls theactions of the extruding head to extrude printing layers of the buildmaterial (as mentioned in 208).

As mentioned above, one or more functional tool heads may act ascorrective devices. These corrective devices may be controlled by thecontroller or a defect feedback controller managing the functions of thecorrective devices to be performed. In an embodiment, the system forprinting a 3D object may comprise the same controller for controllingand generating instructions for the extruding head and the correctivedevices both. In another embodiment, the extruding head and thecorrective devices are controlled by a first controller and a secondcontroller respectively.

Corrective devices are utilized in the build apparatus to correct thedefects formed in a 3D object while it is being printed by the extrudinghead. As may be a case, while printing an object, there may beoccurrence of air bubbles, or excess polymer in the object that may actas a structural defect, a defect reducing the dimensional tolerance ofthe object, and also a defect in mechanical strength of the object. To aperson skilled in the art, there may be a number of different defectsoccurring in printing of the object, such as in structure of object, orin build volume where printing happens, and the like. Thus, to correctsuch defects during printing of the object, the present inventionprovides corrective devices in the build apparatus.

The corrective devices are the functional tool head attachments thatwork on the instructions generated by the defect feedback controller.The instructions are generated in response to the defects detected byone or more monitoring devices, such as quality detecting devices. In anembodiment, the defects that may form during the printing process in theobject may be drooping/sagging, insufficient crystallinity, slowsolidification, out of tolerance feature, air bubbles, excess polymer,delamination, overhangs, warping, adhesion between printed layers of theobject and the like.

The corrective devices for correcting defects are functional based. Inan embodiment, the corrective devices may perform different type offunctions including and are not limited to cooling, heating, milling,deburring, air blowing and the like that are needed to assist theprinting of the object in order to get final printed object with minimaldefects.

The monitoring devices or the quality detecting devices continuouslymonitor (210) and identify the printing defects in the object while itis being printed, in real time. To perform this function, the qualitydetecting device may employ detecting techniques that efficientlyidentify the features of the defects forming in the object, in realtime. In an embodiment, the detecting techniques include and are notlimited to visual imaging, IR/thermal imaging, laser techniques, audiomicrophones, and the like to identify the features of the defects suchas location, type, corrective action, temperature and the like. Thequality detecting devices may include but are not limited to camera,lasers, or any other available image detection devices, infrared devicesto check the geometry of the object, audio microphones to captureabnormal extrusion sounds, which indicates if the filament is properlydried, and the like devices. As the extruding head deposits the actualprintable layer for building the object, the quality detecting devicescontinuously monitor and analyze the deposited layer for errors ordefects, as shown by 210 in FIG. 2.

When the defects are identified by the quality detecting devices, thefeatures of the defects are communicated to the controller, such as adefect feedback controller, where the defects are analyzed andprocessed. Thereafter, a corresponding set of correcting instructionsfor the corrective devices are generated by the defect feedbackcontroller. The functional tool heads attached to the corrective devicesmay control them depending on the correcting instructions, and instructthe corrective devices to perform accordingly. This further means,depending on the defect identified, the defect feedback controller maygenerate correcting instructions and instruct the corrective devices toperform the corresponding function for the specific defect. If anidentified defect is catastrophic (i.e. cannot be corrected to meet theuser's specification), the build may terminate and the defect may berecorded and highlighted in a build report.

In an embodiment of the invention, the quality detecting devices whilemonitoring the printing process may come across situations when thereare no errors in the printing process (shown by 212). In suchsituations, the system 200 may update the printed object model alongwith the slicing parameters and tool path instructions 206 followed bythe tool heads, as shown by 214 in the system 200. On the contrary, thequality detecting devices may detect one or more defects in the printingprocess. Depending on the feature of defects, the system 200 stopsbuilding the object and generates a build report featuring thedefects/errors. This may be the case when the errors are catastrophic(shown by 216).

On the other hand, when the errors are not catastrophic, the defectfeedback controller may generate a set of correcting instructions forrepairing the defects in the printable layer. The system 200 allows forin-situ correction of such defects. Therefore, the functional tool headswith the corrective devices repair the defects according to theirfunctions while the object is being printed. Thereafter, repairing thedefects, the system 200 may update the printed object model along withthe slicing parameters and tool path instructions 206 followed by thetool heads. This is depicted by the part 218 of the system 200. Further,if the printing of the object is completed, the system 200 may generatea build report comprising features of the defects and their correctiveinstructions employed. Furthermore, the optimized slicing parameters aresaved for the next build.

In an embodiment, the identified defects along with the detected buildparameters (for example extrudate width, layer height, etc.) areanalyzed in-situ during the printing process by a slicing feedbackcontroller. The analysis is done in comparison to the intended objectgeometry and properties (for example mechanical, thermal, chemical,electrical, etc.). Based on this analysis, the slicing feedbackcontroller generates a set of slicing instructions. The slicinginstructions adjust the tool path instructions 206 for all subsequentlayers to reduce the future occurrence of defects and ensure that theintended object requirements are met.

In an embodiment of the present invention, a single controller mayperform the functions of the controllers that are the defect feedbackcontroller and the slicing feedback controller for controlling theextruding head and the corrective devices.

In this way, the system may monitor the printing process, in real time,implementing the quality detecting devices to identify defects andgenerate appropriate correcting instructions for correcting the defects,and adjust the tool path instructions for following layers. Thiscorrection process occurs in-situ with the printing of the 3D object.Resultantly, the present invention provides a system for real timemonitoring and identifying the defects occurring in a 3D object usingquality detecting device, while it is being printed, and accordinglytaking appropriate correction measures, using corrective devices tobuild a final build object with minimal defects.

The build device provides independent and automated control of thefunctional tool heads with the extruding head and the corrective devicesbased on the feedback analysis from the quality detecting devices andthe defect feedback controller.

In an embodiment of the present invention, the build apparatus maycontain a single functional tool head having a plurality of attachmentpoints for attachment of a plurality of tools for performing differentfunctions. In case of the build apparatus having a single functionaltool head with attachment points for a plurality of tools, thecontroller sends instructions to the single functional head andinstructs it to choose the desired tool.

Each of the functional tool heads are the working tools of the buildapparatus that are working independently of each other and areautomatically driven based on the instructions received from the userdevice and the defect feedback controller.

While the corrective devices repair the defects during the printingprocess, the slicing feedback controller also analyzes the collectedinformation about the defects and build parameters to determine thein-situ object geometry and object properties (i.e. mechanical,chemical, thermal, electrical, etc.). The in-situ object geometry andproperties are analyzed in comparison to the input object requirementsto generate the appropriate instructions for the slicing engine. Theseinstructions modify the slicing parameters and the resulting tool pathinstructions 206 to reduce the future occurrence of defects and ensurethat the object requirements are met.

The present invention provides a system for generating optimal tool pathinstructions 206 for building a 3D object. Further, the presentinvention provides a build apparatus for real time monitoring,identifying and correcting the defects forming in the 3D object, whileit is being printed, by implementing plurality of quality detectingdevices and corrective devices with multiple degrees of freedom.Furthermore, the present invention provides a system to modify the toolpath instructions 206 in-situ during the construction of a 3D objectbased on the feedback analysis from the data collected by the qualitydetection devices.

For the additive manufacturing process, the extruding head may be fedwith a building material from which the object may be printed. In anembodiment, the building material may be an amorphous polymer, asemi-crystalline polymer, a metal, a ceramic, carbon or other reinforcedmaterial, or the like.

In an embodiment of the present invention, the movement of thefunctional tool head is controlled by the controller. The controller onreceiving the tool path instructions, required for printing the 3Dobjects, control the movement of the functional heads. The movement ofthe functional heads can be done either through Cartesian mechanism orthrough non-Cartesian mechanism. In case of Cartesian movement, thefunctional heads are moved in X, Y and Z-axis and the movements arerestricted to axial movement. In case of Non-Cartesian movement, thefunctional heads are free to move in any axis.

The components of the system 200 will be described in details infollowing figures.

FIG. 3 illustrates a flow diagram depicting a relation between a firstengine, such as a slicing engine and functional tools of a 3D printingmachine, including an extruder, in accordance with an embodiment of thepresent invention. FIG. 3 shows a block diagram illustrating componentsof the system 200 that help in slicing a 3D data file into printablelayers and depositing the layers. To print a 3D object, a user utilizesa user device to input the desired characteristics of the objectrepresented in a 3D data file. The present invention determines slicingparameters and optimal tool path instructions 206 for the object. Fordetermining the optimal tool path instructions 206, the system 200 mayutilize detecting and analyzing tools.

The tool path instructions 206 may be determined based on the slicingparameters and material properties 204 a; and the object propertyrequirements 204 b. The tool path instructions 206 are the instructionsthat may be followed by an extruding tool head in order to print thelayers of a building material to form a 3D object on a build platform.Additionally, the tool path instructions 206 are modified in-situ duringthe construction of a 3D object based on the analysis from the slicingfeedback controller.

The present invention may comprise a slicing engine 300 that considersthe slicing parameters and material properties 204 a and object propertyrequirements 204 b for discretizing a 3D data file 202 of a desiredobject to be printed. The slicing engine 300 discretizes the 3D datafile 202 into a plurality of segments aligned along arbitrary plane. Inan embodiment, the slicing engine 300 may also slice the 3D data file202 into plurality of two dimensional layers for printing. Thereafter,tool path instructions 206 are generated based on the discretizationdone by the slicing engine 300.

The generated tool path instructions 206 are followed by an extrudinghead attachment 306 of the functional tool heads 304, controlled by acontroller 302. Therefore, as the tool path instructions 206 aregenerated, the controller 302 controls the functional tool heads 304 andinstructs them to perform the desired extrusion of building material.Since, the extrusion happens utilizing the extruding head 306,therefore, the functional tool heads activate its extruding head ormounts the extruding head attachment, and instructs it to deposit theprintable layers of building material following the tool pathinstructions 206. In this way, the extruding head 306 deposits aplurality of printable layers under the control of the controller 302,and follows the tool path instructions 206.

The functional tool heads 304 are the automatic working devices of thebuild apparatus having multiple degrees of freedom of motions that printa 3D object and also supports in printing such objects. In anembodiment, the functional tool heads 304 may have more than one, suchas 5 or 6, degrees of freedom of motion.

The extruding head of the build apparatus may be fed with a buildingmaterial of which the 3D object may be build. In an embodiment, thebuilding material may be an amorphous polymer, a semi-crystallinepolymer, metal, ceramic, carbon or other reinforced material.

FIG. 4 illustrates a part of the system 200 for analyzing 3D printedobjects, repairing defects generated during printing, and updatingslicing parameters and printed object model 214, in accordance with anembodiment of the present invention. As described in FIG. 2, besides theextruding head, the other functional tool heads can act as correctivedevices for the printing process. The corrective devices are thoseautomatic working devices of the printing process that may assist theprinting of an object by correcting defects forming in the object, inreal time. During the printing of the object using the extruding head,one or more defects may be formed in the object. In an embodiment, thetype of defects may include but are not limited to drooping/sagging,insufficient crystallinity, slow solidification, out of tolerancefeature, air bubbles, excess polymer, delamination, overhangs, warping,adhesion between printed layers of the object and the like that canresult in insufficient mechanical, chemical, thermal, or electricalproperties of the object.

Further, the system 200 may comprise one or more monitoring devices,such as quality detecting devices 400. The quality detecting device 400may continuously monitor the printing process and identify one or moredefects forming within the object, in real time. In an embodiment, realtime monitoring by the quality detecting devices 400 includes devicethat involves the use of infrared, x-ray, or visual imaging to detectdimensionality and contour of the build; or use of audio microphones todetect if the filament is dry; or defect sensing includingidentification of the type of defects, such as vacancies, excessmaterial deposition, trapped air bubbles, and the like, along with otherfeatures of the defects, such as location of defects, and number ofdefects, and the like. The quality detecting devices 400 also involvemeasurement of critical features of the object to ensure each feature iswithin an acceptable tolerance specified by the user.

The quality detecting devices 400 may make use of detecting techniquesfor real time monitoring the building process and identifying thedefects in the object. In an embodiment, the detecting techniquesincludes and are not limited to visual imaging, IR/thermal imaging,laser techniques, audio microphones, and the like to identify thefeatures of the defects such as location, type, correction action,temperature and the like.

While the 3D object is being printed by the extruding head, the qualitydetecting devices 400 in the build apparatus keep a continuous check onthe printing process and monitor the process in real time. Therefore,the quality detecting devices 400 may identify the defects forming inthe object, by implementing various detecting techniques. Afteridentifying the defects, the quality detecting devices 400 may store thecaptured data in a data storage module, where the data defines thefeatures of the defect, such as location, type, etc., critical featuremeasurements, dimensionality, and contour of the build object. Thus, thepresent invention provides recording and logging of real time events,such as defects, corrections, location of each defect in 3D space, andrecording of modifications to the object model and slicing parameters.

Thereafter, the detected data may be transferred to a controller, suchas a defect feedback controller 402 that implements analyzing tools topredict a set of correcting instructions 404. The correctinginstructions are the steps that should be taken to correct the defectsand predict the properties of the object considering the types of defectidentified by the quality detecting devices 400. In an embodiment, thedefect feedback controller 402 may be a correction module that analyzesthe collected data from the quality detecting devices 400 and generatesa feedback (including correcting instructions 404) depending on thefeatures of the defects. In another embodiment, a slicing feedbackcontroller 408 analyzes the collected information about the defects andbuild parameters to determine the in-situ object geometry and objectproperties (i.e. mechanical, chemical, thermal, electrical, etc.). Thein-situ object geometry and properties are analyzed in comparison to theinput object requirements to generate the appropriate slicinginstructions 410, depending on the defected data, for the slicing engine300. These slicing instructions 410 in-turn modify the tool pathinstructions 206 to reduce the future occurrence of defects and ensurethat the object requirements are met.

In an embodiment, the system 200 for printing a 3D object comprises asingle controller that controls and generates instructions for both theextruding head and the corrective devices.

The defect feedback controller 402 may determine the properties of theobject being printed and the correcting instructions 404, based on thedefects identified and the desired strength needed in the object.Further, the defect feedback controller 402 may instruct the correctivedevices to perform their corresponding functions based on the correctinginstructions 404. The determined correcting instructions 404 may be fedto the controller 302 that further controls the functional tool heads304. After receiving the correcting instructions 404, the functionaltool heads 304 instruct their required tool head attachments, which arecorrective devices 406 here, since correcting instructions are needed.Resultantly, the corrective devices 406 perform the required functionsbased on the correcting instructions 404 in order to correct thedefects/errors occurring in the printing.

In an embodiment, the corrective devices 406 are attached to thefunctional tool heads 304 to perform a type of function for correcting acorresponding defect, where the type of function may include cooling,heating, milling, deburring, air blower, and the like that are needed toassist the printing of the object in order to get final printed objectwith minimal defects. Therefore, the correction devices 406 may performa function required to correct a corresponding defect.

For an instance, if the quality detecting devices 400 identify that theprinted layers of the build material are not adhering properly with eachother, and it is resulting in inaccurate geometry, reduced mechanicalstrength, reduced thermal or electrical conductivity, or the like of theobject, the defect feedback controller 402 determines that the printingprocess needs heating of the deposited build material for properadhesion of the layers. Thus, the defect feedback controller 402 maydetermine ‘heating’ as the correcting instruction 404 and instruct acorresponding corrective device (406) to perform heating of thedeposited layers to ensure proper adhesion. Based on the identifieddefect, the slicing feedback controller 408 may modify the slicinginstructions 410 in order to further modify the tool path instructions206 for reducing the future occurrence of defects and ensure that theobject requirements are met. For this instance, the modified slicinginstructions may involve decreasing the layer height, increasing thematerial feed rate, and/or increasing the extrudate width.

Therefore, the system 200 provides real time monitoring of the printingprocess and identifies the defects forming in the object, byimplementing quality detecting devices 400. Further, the controller 302provides independent and automatic control of the corrective devices,based on the feedback analysis, in order to correct the defects in theobject and modify appropriate tool path instructions 206, in real timeand resultantly have a 3D object with minimal defects.

In an embodiment of the present invention, the build apparatus maycontain a single functional tool head 304 having a plurality ofattachment points for attachment of a plurality of tools performingdifferent functions. In case of the build apparatus having a singlefunctional tool head with attachment points for a plurality of tools,the controller may send instructions to the single functional head andinstructs it to choose the desired tool.

In another embodiment of the present invention, the functional toolheads may be attached to a plurality of tool attachments wherein themovement of the plurality of tool attachments is controlled by thecontroller. Each of the plurality of tool attachments contains anattachment point which provides an attachment mean to the functionaltool head 304 required for different functionalities in 3D printingprocess. Each of the tool attachments or arms are the working tools ofthe build apparatus that are working independently of each other and areautomatically driven based on the instructions received from thecontroller 302 and the defect feedback controller 402.

Further, while simultaneously printing the object using the firstfunctional heads and correcting the defects in the object, the printingsystem also provides a build report. After the completion of the processof printing the object and correcting the defects, a build report may begenerated at the user device. Based on the feedback from the printingand correcting processes, a build engine of the user device may generatea build report visually displaying, in 3D space, each corrected anduncorrected defect detailing its type and location within the object.The defect information in the build report is utilized by an analyzingmodule of the user device to predict the material properties of thefinal object based on the type, number, and location of corrected anduncorrected defects. The analyzing module may implement analyzingtechniques, such as finite element analysis.

The build report also compares the actual material properties of thefinal object compared to the user's inputted specifications andidentifies any properties that fall outside the specifications, byimplementing analyzing techniques. The information in the build reportmay help a user to decide whether to keep the final object or scrap theobject based on the resultant properties acquired in the final printedobject and the features of the corrected and uncorrected defects. Thisstep is a critical step in identifying the worth or suitability of thefinal object for its intended use.

Further, in an embodiment, the build report may also help in resolvingthe mechanical or thermal behavior and uncorrected defects of the builtobject when it may be re-printed using the similar building constraintsand parameters. Thus, the generation of the build report may aid in theoptimization of the tool path instructions 206 when printing the same orsimilar objects with desired properties and also help in deciding theworth of the final printed object. Therefore, an analyzing technique,such as finite element analysis, may be run on the build report topredict the material properties of the final object and decide whetherto keep or scrap the final object based on the resultant properties.

FIG. 5 illustrates a table showing the types of defects, the techniqueby which it is detected and suggested course of action for correctingthe defect, in accordance with an embodiment of the present invention.The column 502 shows the defects that may occur while a 3D object isbeing printed. During printing, a defect might occur, for exampledeposition of excess polymer by the first robotic manipulator. This typeof defect may be detected by Visual Imaging, Laser (504). Thereafter,the defect feedback controller 402 may determine the course of action(correcting instructions) that may include deburring, radiative heating,or tamping (506). This course of action is then signaled to theappropriate functional tool head 304 that performs either deburring, orradiative heating, or tamping. The defect feedback controller 402provides instruction to the required functional tool head 304 and thefunctional tool head 304 performs the function through its movement inx, y and z axis. The movement of functional tool head 304 is requiredfor correcting the defects in 3D manner. In an embodiment of the presentinvention, the movement of functional tool head 304 can be performedeither in Cartesian mechanism where the tools heads are moved by thedirectional coordinates in X, Y and Z direction, or it can be throughnon-cartesian mechanism wherein the functional tool heads 304 can movein three dimensional space freely.

The slicing feedback controller 408 may also generate slicinginstructions 410 to prevent excess polymer from being deposited insubsequent layers. In this instance, the slicing instructions mayinvolve increasing the layer height, decreasing the material feed rate,and/or decreasing the extrudate width. In this way, a number of defectsmay be detected during the printing process by a variety of qualitydetecting techniques and hence, a variety of correcting instructions 404and slicing instructions 410 may be determined by the feedbackcontrollers 402 and 408.

FIG. 6 illustrates an exemplary illustration wherein the functional toolheads 304 are attached to a plurality of tool head attachments 604 usedin the additive manufacturing method. As shown in FIG. 6, eachfunctional tool head 304 may have a tool attaching point 602. The toolattaching point 602 may be utilized to fix a tool head attachment 604 tothe functional tool head 304 that performs a specific functionality. Thefunctional tool heads 304 are the automatic working devices for theprinting process to perform desired functions. Each of the functionaltool head 304 may be equipped with a tool head attachment 604 thatperforms a specific function and is attached to the tool attaching point602 of the functional tool head 304. It might also be a possible case,where the functional tool head 304 may pick up a variety of fixtures,where the fixtures act as tool head attachments, performing differentfunctionalities, and are attached to the functional tool head 304 viathe tool attaching point 602.

Therefore, if a functional tool head 304 is instructed to performcooling, it may pick up a fixture or tool head attachment 604 thatperforms the cooling function and attaches the particular tool headattachment 604 via the tool attaching point 602. Thereafter, if the samefunctional tool head 304 is instructed to capture a thermal image, itmay drop the cooling tool head and pick up a new fixture or tool headattachment 604 that works as a thermal imaging device and attaches theparticular tool head attachment 604 via the tool attaching point 602. Inthis way, the functional tool head 304 may interchange the functionalityaccording to the need of the printing process.

In another embodiment, the functional tool heads 304 may performdedicated functions, such as depositing build material, heating,cooling, blowing air, milling, deburring, laser heating, and the like.Therefore, each functional tool head 304 attaches the corresponding toolhead 604 via the tool attaching point 602.

FIG. 7 illustrates a flowchart showing a method of additivemanufacturing to print a 3D object with real time process monitoring,identifying and correcting defects in the printed 3D object, inaccordance with an embodiment of the present invention. At step 702, auser may input a 3D data file 202 using a user device, where the 3D datafile defines the characteristics of a 3D object. In an embodiment of thepresent invention, the user device may be a computing device, includingand is not limited to a computer, that may further include 3-D modelingsoftware, such as AutoCad and the like. In a further embodiment, the 3Ddata file may include and is not limited to a CAD file, or an STL file,or a COD file, and the like. In another embodiment, characteristics ofthe object may include and is not limited to structural geometry of theobject, inherent material properties, such as mechanical, electrical,chemical, and thermal properties, and the like. In a further embodiment,the additive manufacturing method is an extrusion based printing methodor continuous fiber based deposition processes, including and notlimited to fused deposition modeling, fused filament fabrication and thelike; and other methods, such as droplet based, jetting methods and thelike.

After receiving the 3D data file 202, a first engine, such as a slicingengine 300 discretizes the 3D file 202 into a plurality of segmentsalong arbitrary planes, at step 704. Additionally, the slicing engine300 is also capable of discretizing the 3D data file 202 into a numberof slices along two dimensional planes. Following slicing of the file202, at step 706, a set of tool path instructions 206, therefore, arethen formulated using the slicing engine 300 depending on a set ofslicing and material parameters 204 a and object property requirements204 b. The tool path instructions 206 are also adjusted in-situ by theslicing feedback controller to reduce the future occurrence of defectsand ensure that the object requirements are met.

The build apparatus may comprise a plurality of functional tool heads304 with a plurality of tool head attachments possessing multipledegrees of freedom of motion for printing a 3D object and also assist inthe printing process. In an embodiment, the functional tool heads 304with attachments may possess more than one, such as 5 or 6, degrees offreedom of motion. The functional tool heads 304 are the working devicesof the printing process described in the present invention that workindependently and automatically of each other, based on a feedbackanalysis generated from the system. Further, one or more of the toolhead attachments may act as print head, or extruder, or deposition headfor depositing layers of build material to print a 3D object on theprinting platform in the build apparatus. The tool head attachmentsworking as deposition head may be hereinafter referred to as extrudinghead 306 that may be controlled by a controller 302. The controller 302remains in communication with the user device for receiving tool pathinstructions 206. Therefore, at step 508, the controller may instructthe extruding head 306 to follow the tool path instructions 206 anddeposit the printable layers of a building material to build the 3Dobject.

In an embodiment, the movement of the functional tool head 304 iscontrolled by the controller 302. The controller 302, on receiving thetool path instruction 206 required for printing the 3D objects, controlsthe movement of the functional heads. The movement of the functionalheads 304 can be done either through Cartesian mechanism or throughnon-Cartesian mechanism. In case of Cartesian movement, the functionalheads 304 are moved in X, Y and Z-axis and the movement is restricted toaxial movement. In case of Non-Cartesian movement, the functional heads304 are free to move in any axis.

While the extruding head 306 is working continuously to deposit layersof build material on the printing platform to print the object, theremay occur an instance when the printing may possess one or more defectsin the object that may further lead to faults in geometry or inherentproperties of the object, such as low mechanical strength. In anembodiment, the type of defects may include and are not limited todrooping/sagging, insufficient crystallinity, slow solidification, outof tolerance feature, air bubbles, excess polymer, delamination,overhangs, warping, adhesion between printed layers of the object andthe like that can result in insufficient mechanical, chemical, orthermal, or electrical properties of the object.

In order to detect such defects, in real time, while the printingprocess is happening, the system comprises one or more monitoringdevices, such as quality detecting devices 400, to continuously monitorthe printing process. The quality detecting devices 400 may employdetecting techniques to perform the detection of defects in 3D objectbeing printed. The detecting techniques include and are not limited tovisual imaging, IR/thermal imaging, laser techniques, audio microphones,and the like to identify the features of the defects such as location,type, correction action, temperature and the like. Therefore, at step710, the quality detecting devices 400 may continuously monitor theprinting process and identify the defects forming in the object, byimplementing the detecting techniques. The quality detecting devices 400may include and are not limited to thermal sensors, cameras, lasers, orany other available image detection devices, infrared devices to checkthe geometry of the object, audio microphones to capture abnormalextrusion sounds, which indicates if the filament is properly dried, andthe like devices.

Further, the method of the present invention also provides a mechanismfor real time correction of the defects that are occurring while theobject is being printed. To accomplish this, one or more of thefunctional tool heads 304 may act as corrective devices 406 fixing thedefects identified by the quality detecting devices 400. Therefore, oneor more corrective devices 406 are the tool heads to perform one or morefunctions for correcting one or more defects, where the type offunctions may include cooling, heating, milling, deburring, air blower,and the like that are needed to assist the printing of the object inorder to get final printed object with minimal defects.

As soon as the quality detecting devices 400 identify the defects, andtheir features, such as location and type of defects location, they maystore the defects data in a data storage module, where the data definesthe features of the defect, such as location, type etc., criticalfeature measurements, dimensionality, and contour of the build object.Thus, the present invention provides recording and logging of real timeevents, such as defects, corrections, location of each event in 3Dspace.

Thereafter, the detected data from the quality detecting devices 400 maybe fed to a controller, such as a defect feedback controller 402. At thefeedback controller 402, the defected data is analyzed to furthergenerate a set of correcting instructions 404 that should be taken tofix the defects. In an embodiment, analyzing software, such as finiteelement analysis, may predict the properties of the object consideringthe types of defect identified by the quality detecting devices 400.Therefore, the defect feedback controller 400 may act as a correctionmodule that generates feedback (correcting instructions 404) dependingon the features of the defects.

Thereafter, generating the correcting instructions 404, the defectfeedback controller 400 may control the corrective devices 406 andinstruct them to perform corresponding functions based on the feedback,generated including the correcting instructions 404. Therefore, at step712, the correction devices 406 function automatically and independentlyof each other in-situ correcting the defects formed in the 3D objectduring printing process, following the correcting instructions 212.

At step 714, considering the defected data from the quality detectingdevices 400, a controller, such as a slicing feedback controller 408,may modify the implemented slicing instructions 410 for the slicingengine 300 to further discretize the 3D data file 202. The modifiedslicing instructions 410 in turn modify the tool path instructions 206to reduce the future occurrence of defects and ensure that the objectrequirements are met.

After the completion of the printing and correcting process, a buildreport may be generated at the user device (step 716), based on theprinting and the correction of defects. Based on the feedback from thebuild volume, where printing and defects correction are simultaneouslyoccurring, the user device may generate a build report visuallydisplaying in 3D space the features of the final printed object and alsoeach corrected and uncorrected defect detailing its type and locationwithin the object. The defect information in the build report may beutilized by an analyzing module of the user device to predict thematerial properties of the final object based on the type, number, andlocation of corrected and uncorrected defects. This report also comparesthe actual material properties of the final object with the user'sinputted specifications and identifies any properties that fall outsidethe specifications.

Furthermore, the information in the build report may help a user todecide whether to keep the final object or scrap the object based on thepredicted inherent properties and the features of the corrected anduncorrected defects. This step is a critical step in identifying theworth of the final object. Further, the build report may also help inresolving the mechanical or thermal behavior and uncorrected defects ofthe built object when it may be re-printed using the similar buildingconstraints and parameters. Thus, the generation of the build report mayaid in the optimization of the tool path instructions 206 when printingthe same or similar objects with desired properties and further helps auser in knowing the worth of the final printed object.

Therefore, the present invention provides a system and a method of threedimensional printing, where the printing process is monitored in realtime for identifying any defects forming in the 3D object. Further, thepresent invention provides in-situ correction of identified defects,during printing, by independent and automated control of functional toolheads based on a feedback analysis from the printing process.

Following example may be helpful in order to understand the presentinvention clearly.

In one manifestation of this present invention, a 3D printing machineinvolves two independently controlled multi-axis functional tool heads.Say those functional tool heads may be robotic arms, where robotic arm Xconsists of an extruder and robotic arm Y functions as a real-timecorrection device.

Robotic arm X is controlled by the tool path instructions 206 generatedfrom the CAD file.

Robotic arm Y can employ a number of interchangeable fixtures to correctdefects during part manufacturing. Considering, ‘B’ and ‘C’ defects aredetected real-time using a multi-axis system consisting of D devicesduring build production, where D devices are quality detecting devices.Image processing software identifies the type, location, and number ofdefects present. This information is fed into the controlling software(feedback controller) for robotic arm Y, which identifies theappropriate course of action to correct the defect; some defects are notcorrectable by robotic arm Y but are still logged in the data storagemodule. This information is fed into a final build report.

Further, Robotic arm Y picks up the appropriate fixture with ‘A’functionality to correct the defect. At this time, robotic arm X cancontinue to extrude material if the deposition site is not affected;otherwise, robotic arm X waits until robotic arm Y has finishedcorrecting the defect. The defect information is used to update theprinted object model and slicing parameters. As a result, the subsequenttool path instructions are modified for robotic arm X. Robotic arm Yrepeats the above operation to correct every possible defect during theentire build process.

When the build process is complete, the build report is generated, whichvisually displays each defect detailing its type and location within thepart. This information is used to predict the material properties of thefinal part based on the type, number, and location of corrected anduncorrected defects.

In an embodiment, the functionality ‘A’ can be cooling, heating,milling/deburring, and the like. In an embodiment, the defect ‘B’ can bedrooping/sagging, insufficient crystallinity, slow solidification, outof tolerance feature, and the like. The defect ‘C’ air bubbles, excesspolymer, delamination, overhangs, warping, adhesion between printedlayers of the object and the like.

In an embodiment, the quality detecting device ‘D’ can be visualimaging, IR/thermal, laser techniques, audio microphones, and the like.

1-21. (canceled)
 22. A method for printing a three-dimensional (3D)object, comprising: (a) providing a printing instruction generated basedat least in part on (i) a model of said 3D object and (ii) a one or moreprinting parameters; (b) initiating printing of a part corresponding tosaid 3D object using said printing instruction; (c) using one or moremonitoring devices to detect for one or more defects from said partwhile printing said part corresponding to said 3D object; and (d)generating a correcting instruction to correct for said one or moredefects while printing said part.
 23. The method of claim 22, furthercomprising, prior to (a), providing a data object comprising said one ormore printing parameters.
 24. The method of claim 23, wherein, in (a),said providing said printing instruction comprises discretizing saiddata object into a plurality of segments to generate said printinginstruction.
 25. The method of claim 22, further comprising using saidcorrecting instruction to modify said printing instruction, therebygenerating a modified printing instruction.
 26. The method of claim 25,further comprising using said modified printing instruction to modifysaid part.
 27. The method of claim 22, further comprising sending saidcorrecting instruction to at least one corrective device for correctingsaid one or more defects while said part is being printed.
 28. Themethod of claim 27, wherein said at least one corrective device performsone or more functions selected from the group consisting of cooling,heating, milling, deburring, and extruding.
 29. The method of claim 22,further comprising generating a build report comprising at least onefeature of said one or more defects.
 30. The method of claim 29, furthercomprising analyzing said build report to determine one or more finalproperties of said part.
 31. The method of claim 22, further comprisinglogging real time monitoring data of said one or more defects in a datastorage module.
 32. The method of claim 22, wherein said one or moredefects includes a void, and wherein said correcting instruction includeinstruction for correcting said void.
 33. A system for printing athree-dimensional (3D) object, comprising: an instruction engineconfigured to generate a printing instruction for printing said 3Dobject; one or more print heads to print a part corresponding to said 3Dobject using said printing instruction; one or more monitoring devicesfor detecting of one or more defects in said part during printing; acontroller operatively coupled to said one or more print heads and saidone or more monitoring devices, wherein said controller is configuredto: (i) use said one or more monitoring devices to detect for said oneor more defects while printing said part; and (ii) generate a correctinginstruction to correct for said one or more defects while printing saidpart.
 34. The system of claim 33, wherein said controller is furtherconfigured to communicate with said instruction engine and instruct saidinstruction engine to use said correcting instruction to modify saidprinting instruction.
 35. The system of claim 33, further comprising amodule configured to (i) generate a build report comprising at least onefeature of said one or more defects; and (ii) analyze said build reportto determine one or more final properties of said part.
 36. The systemof claim 35, wherein said module is configured to analyze said buildreport using finite element analysis.
 37. The system of claim 35,wherein said build report comprises an identification of one or moreproperties of said part that falls outside of one or more specificationsof said 3D object.
 38. The system of claim 33, further comprising a datastorage module configured to record data indicative of said one or moredefects of said part.
 39. The system of claim 33, wherein saidcorrecting instruction comprises cooling, heating, milling, deburring,or extruding instruction.
 40. The system of claim 33, wherein said oneor defects includes a void, and wherein said correcting instructioninclude instruction for correcting said void.
 41. The system of claim33, wherein said one or more monitoring devices employ visual imaging,thermal imaging, or laser-based detection.